Animal Bodies

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Animal Bodies

• Chapter 34
• Section 2

2
Body Structure

• Symmetry-a consistent overall pattern of
  structure-is displayed by some animals and is not
  present in others.
• Animal bodies range from those that lack true
  tissues and an organized body shape, to those
  that have very organized tissues and a consistent
  body shape.

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Patterns of Symmetry

• Some animals have no front, back, right or left
  end, but have a top and bottom side
• Radial Symmetry-an arrangement of body parts
  around a central axis
• Most animals have dorsal and ventral side,
  anterior and posterior end, and a right and left
  side
• Bilateral symmetry-two similar halves on either
  side of a central plane
• Cephalization is the concentration of sensory and
  brain structures in the anterior end of the
  animal

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Bilateral Symmetry (Butterfly)
Radial Symmetry (Hydra)
5
Germ Layers

• Germ layers- a specific layer of cells in an
  embryo from which specific organ systems are
  derived
• Occurring from these germ layers is every body
  feature, organ and tissue.

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Body Cavities

• A body cavity is a fluid filled space that forms
  between the digestive tract and the outer wall of
  the body during development
• A body cavity aids in the movement process by
  muscles contracting against a firm structure
• The fluid in a body cavity transports nutrients
  and wastes.

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Animal Diversity

• A phylogenetic tree of animals shows the
  evolutionary relationships thought to exist among
  11 major animal phyla.
• Multicellularity and a limited degree of cell
  specialization characterizes sponges.
• True tissues in two layers are found in
  ctenophores and cnidarians.
• True tissues in three layers and bilateral
  symmetry are all other animal phyla.

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Invertebrates

• A heterogeneous group that range from no body
  symmetry or true tissue, to bilateral symmetry
  and specialized body parts.
• The trait that connects all invertebrates is the
  absence of a backbone
• Are a large number of animals species as well as
  most individual animals.

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10
Chordates

• Chordate- an animal that, some day, has a dorsal
  nerve cord, a notochord, and pharyngeal pouches
• Notochord- a firm, flexible rod of tissue in the
  dorsal region.
• Dorsal nerve chord- a hollow tube just above the
  notochord
• Pharyngeal pouches- small out pockets of the
  anterior part of the digestive tract.
• Postanal tail- muscle tissue that lies behind the
  posterior opening of the digestive tract.

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Chordates Continued

• Regularly in vertebrates, a subphylum of the
  chordates, the dorsal nerve cord, develops in the
  brain and the spinal cord and runs in the back
  bone.
• Fish and amphibians develop their pharyngeal
  pouches into gills.
• In most vertebrates, the notochord evolves when
  they are an embryo and replaced by a backbone
  later in development.

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Vertebrates

• Humans are vertebrates, and interact with other
  vertebrates.
• Fish and birds, along with many other animal
  species, are a food source for humans.

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